Direct Electrical Heating (DEH) of subsea pipelines for gas production is a widely used method for preventing hydrate plugs in gas pipelines. The method is based on injecting a single phase AC current direct through the gas steel pipe and back through a cable strapped on the top of the pipe. This method can limit the use of inhibitors, such as methanol. The conventional way to create a single phase power supply suitable for the load (pipeline), is to use a 3 phase transformer with a balancing/compensating circuit on the transformer secondary windings. The balancing/compensating circuit has two capacitors and one inductor connected between the three different phases. The transformer will be subjected to a symmetrical three phase load with power factor close to 1, if these three impedances are properly matched to the pipeline impedance.
Do to the mentioned properties of the DEH system, the balancing circuit has drawbacks:                Complex fine tuning of the circuit needs to be done during commissioning.        High short circuit levels are seen at the single phase source terminals (e.g., danger of damage to the pipeline by burning hole in the pipeline in case of short circuit)        Transformer with tapping is needed to change the heating power.        Only the grid frequency is available in all modes        